Abc's nick schrifrin leading us out. Now to the other airline scare, the airline forced to lane on the tarmac, after a passenger said the that there was a bomb in his bag. Abc's gio benitez on the brave flight crew jumping into action. Reporter: Last night's air scare started on a 6:30 p.M. Flight from knoxville to denver. A frontier airlines plane, with 136 passengers onboard, was making its descent into denver when a man tells a flight attendant that he has a bomb in his carry-on bag. You could see all of the worried looks as soon as he said it. Reporter: Flight attendants took that bag from the man and brought it to the back of the plane, covering it with seat cushions. Children onboard were moved to the front of the plane. Passengers kept an eye on the man and tried to stay calm. From that point on, we were just extremely scared and worried. Reporter: Tension lasting about a half-hour until that plane was safely on the ground with fbi agents and the denver bomb squad already waiting on the tarmac. Before you know it, authorities boarded the plane. Reporter: And law enforcements haven't identified the suspect only that he's in custody. And he's believed to quote, mentally unstable. Sources tell abc news they didn't find a device on that plane, but boy, david, that was scary.

This transcript has been automatically generated and may not be 100% accurate.

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